Shorting plug and wrench



July 7, 1953 G.r A. KUMPF sHoRTING PLUG AND WRENCH Filed Jan. 50, 1948 nventor y (Ittorneg Patented July 7, 1953 George A. Kumpf,`Erlton, N. J .,-assignorto Radio v'Corporation 'of America, a` corporation of .Dela- Ware Application `January '30, 1948, 'Serial'Nm 5,429

:4 Claims. 1

This invention relates to an improved snortingplug and wrench assembly for `altering the `effective mechanical length and Vhence the "electricaltuning of a transmission line-'ofthe type-coinprising 'concentrically spaced `inner and outer conductors.

The principal object of the'present inventionis to provide a shorting-plug having the minimum number'of parts requiredto effect an adjustable connection'of low impedance between the n'spaced' yapart conductors'of a Icoaxial cable, or the like, and one 'which maybe easily adjusted by a removable wrench of simpleconstruction.

The invention will'be ldescribed inconnection with the accompanying drawing wherein:

Fig. 1 is an exploded'view'of an `open-end Ypor` tion o'fa coaxial cable containing-a bipart shorting-plug which is constructedin'accordance with the principle of the'invention.

Fig. 2 is La view in perspective of the -bi-part snorting-plug of Fig. 1 with its two r-partsa'ss'embled and showing the end vof awrenchifor effecting relative movement ofthesaid parts,

Fig. 3 is a longitudinal sectional vView ntaken 'on the line III-III of Fig. 4of a vcoaxial transmission line with the plug of the invention-arranged therein and with the wrench in Vpositi'onto adjust the plug at a selectedpoint in lthe line and Fig. '4 is a lsectional View taken on thefline IV-*IV'of Fig. 3.

1n the drawing, A designates the outer conductor .and B the inner .conductor of la coaxial cable, side-band iilter, or analogous device capable of handling radio waves of -aj-frequency determined, at least in part, by the eiective length y of the said conductors. The shorting plug .of the invention, shown generally at C, is movable inthe space between the inner and outer conductors and normally constitutes a conductive connection between the said conductors 4A and B. As will hereinafter more -iullyappear the force required to .move the plug toa-desired point Within the cable, and the relative movement of the parts required to secure the plug at that point, are applied by means of a removable socket type wrench D.

As previously indicated the shorting plug C of the invention consists of but two separable parts. These parts comprise a hollow spring ngered chuck I for gripping the inner conductor B and a spring fingered collet 2, surrounding the chuck and adapted to bear against the inner surface of the outer conductor A when the collet is screwedup over the chuck on complementary threads 3 and 4 on the said parts.

It willbe observed upon inspection of Fig. l

that thechuck -I comprises a hollow sleeve which terminates at its inner end in a hexagonal nut portion 5 and, at its outer end, in 'an expanded frusto-conical yportion 'I which is-divided into a number -(in this fcase, eight) of spring-ngers la; Tb, Ic lbyslits "Is which extend from the annular end or -base o'f the cone into the cylindrical central body portion 9 of the sleeve. The threads -3' upon which the outer collet rides are contained on the central body portion 9 of the'chuck ad` jacent to the hexagonal end 5 thereof.

'The outer member or collet '2 of the shor'ting"A plug C5 has a central "cylindrical 4body portion Yii and, like the chuck I, has an expanded frustoconical end portion 8. Here, however, the outer surface VVof fthe ends of the spring fingers "Ea, Sh etc. -whichcomprise the said frusto--conical portion vIl terminate in short cylindrical surfaces 6m, 6u etc. which vprovide an enlarged area oi contactbetween the said ngers and the `inner surface of the'outer conductor A.' As shown in Fig. 3 the threads 4ll which engage the external 'threads 3 yon the chuck `I -are contained on the" 1nner surface of the cylindrical portion A'Ii Noi' the collet. VThevcollet is `also providedg'on its inner end, with an integral cylindrical collar 'portion II) having a radially extending bayonet pin I2 thereon which isadapted to vbe engaged by a complementary bayonet slot AI9 on the socketend I5 of the wrench D. outer diameter of the collar portion Iil'ofthe collet 2 is small enough to permit the slot I3 on the end of the wrench D to be'tted on the pin I2 when the entire plug (C) is within the cable AB. It will also be observed upon inspection of Fig. 3 that the inner diameter ofthe collar portion I0 of the -collet `2 is sulciently large to accommodate an inner hexagonal socket portion I'I of -the wrench which ts over the lhexagonal nut portion5of=the chuck I.

As shown in vlligfl the wrench D comprises an inner `cylindrical member I9 which is supported for rotationfason oneor more insulating spacers or bearings 2i and 23, within an outer cylindrical member 25. The free end of the inner cylinder I9 extends beyond the corresponding end of the outer cylinder 25 and the end of each is provided with an insulating handle 2l and 29, respectively, for holding the one part while turning the other.

As previously indicated, the leading end of the It should be noted'that the delineati 3 provided with a slot I3 within which the pin I2 on the collet ts.

The operation or the device of the invention is as follows: With the collet 2 screwed but part way on the chuck I the flexible fingers 6c, Gb etc., la, 'Ib etc. are free from any clamping force, hence the entire plug may be entered into the cable by fitting the inner fingers Tc, lb etc. over the free end of the inner conductor B and pushing the plug inwardly a convenient distance prior to grasping it with the wrench D. The wrench which, if necessary, may be several feet long, is then fitted over the trailing end of the plug so that its inner socket Il receives the hexagonal nut 5 on the chuck. I and slot IS on the outer cylinder 25 receives. the bayonet pin I2 on the collet 2. When the plug C has been pushed inwardly to the point required to tune the line AB to a desired frequency the plug may be ,tight-` ened at that point simply by holding one of the handles 21 or 25 of the wrench and turning the other handle in the direction required to cause the irusto-conical end or" the chuck I 'to nest tightly within the similarly shaped end of the collet 2. This relative inward movement of the chuck exerts an expansion force upon the spring fingers 6a, 6b etc. oi' the collet 2 and urges the outer cylindrical surfaces 6m, (in etc. of the said fingers into tight engagement with the inner surface of the outer conductor. The same (inn ward) movement of the chuck l compresses its spring ngers la, 'Ib etc. which are thus caused to exert a clamping force upon the inner conM ductor B of the transmission line. It will be apparent that without such positively applied clamping forces it is practically impossible to achieve a low impedance connection between the inner and outer conductors or the line A--B- In order to release the clamping forces applied to the conductors A and B by the chuck i and collet 2 it is merely necessary partly to unscrew the chuck by turning the wrench in the reverse direction, whereupon the plug may be pushed (or pulled) along the inner conductor to any desired point in the line.

From the foregoing it will be apparent that the present invention provides an adjustable snorting plug capable of effecting a connection of extremely low impedance between the inner and outer conductors of a concentric transmission line, and one characterized by its ease of adjustment and by the simplicity and economy of its parts.

What is claimed is:

l. A device for altering the electrical length of a transmission line of the type comprising spaced inner and outer concentric conductors, sai-l device comprising a nest of two complementary, resilient frusto-conical members ccncentrically mountable in the space between said conductors, said members being movable with respect to each other in relative inward and outward nesting movements, whereby said expansible members are urged into and out of engagement with said inner and outer conductors as determined by the direction of said relative nesting movement.

2. A shorting-plug for a transmission line of the type comprising spaced inner and outer concentric conductors, said plug comprising an expansible frusto-conical collet adapted to be accommodated in the space between the said inner and outer conductors, a complementary expan-` sible chuck mounted i'or axial movement within said collet about the outer surface of said inner conductor, screw means for moving said chuck selectively inwardly and outwardly with respect to said collet, whereby to expand said collet and to contract said chuck into clamping engageu ment, respectively, with said inner and outer conductors upon said inward movement of said chuck and to contract said collet and expand said chuck out of clamping engagement with said conductors upon movement of said chuck in said outward direction.

3. A device for altering the electrical length of a transmission line of the type comprising spaced inner and outer coaxial conductors, said device comprising an inner frusto-conical member having external threads and a bore withinV which said inner conductor is adapted to be received, said inner member terminating at its leading end in a plurality of outwardly extending resilient fingers and at its trailing end in a non circular nut portion, and an outer truste-conical member having complementary internal threads and a bore within which said externally threaded inner member is received, said outer member terminat ing at its leading end in a plurality of outwardly extending resilient fingers against which the iingers of said inner member are adapted to bear with a force determined by the relative longitudinal axial position of said members, said outer member being provided adjacent to its trailing end with a radially extending bayonet pin, and wrench means for applying torque to said inner and said outer members through said nut and bayonet pin wherebyto alter said relative longitudinal axial position of said members.

1i. The invention as set forth in claim 3 and wherein said wrench means comprises inner and outer tubular members supported for relative movement about a common axis and terminating respectively at ltheir leading ends in a socket lfor said nut and a bayonet slot for said bayonet pin.

GEORGE A. KUMPF.

References Cited in the file of this patent 'UNITED STATES PATENTS Number Name Date 1,165,273 Miller Dec. 2l, i915 2,203,806 Wolf June 11, i940 2,453,994 Lappin et al Nov. 16, 1948 2,477,232 Branson July 26, 1949 FOREIGN PATENTES Number Country Date 579,276 Great Britain July 30, 1946 

